1. Field of the Invention
The present invention relates to control devices capable of controlling electric rotary machines as a drive power source of motor vehicles.
2. Description of the Related Art
For example, a patent document, Japanese patent laid open publication No. 2002-27611 shows a control device for controlling such an electric rotary machine. The control device is applied to a motor vehicle equipped with an electric rotary machine and an internal combustion engine which are used as drive power sources of a motor vehicle. This control device instructs the electric rotary machine to increase its generated torque when receiving a start request to start the internal combustion engine while the motor vehicle drives by the power of the electric rotary machine. In more detail, the control device increases the output torque of the electric rotary machine by a torque which is obtained by adding a motoring torque and an inertia torque together. The motoring torque is determined on the basis of a target rotation speed of the internal combustion engine, and the inertia torque corresponds to a change rate of the rotation speed of the internal combustion engine.
By the way, there is another type of the control device capable of calculating an instruction torque, to be supplied to an electric rotary machine, on the basis of the target rotation speed of the electric rotary machine, and which drives the electric rotary machine on the basis of the calculated instruction torque. This instruction torque is adjusted on the basis of a correction torque which is calculated on the basis of the change rate of the target rotation speed of the electric rotary machine per predetermined time, and the inertia of a rotary body which contains the electric rotary machine. This makes it possible to improve the followability of an actual rotation speed of the electric rotary machine to the target rotation speed.
When the instruction torque is limited in the control device performing the rotation speed control on the basis of the target rotation speed, it becomes difficult for the actual rotation speed of the electric rotary machine to follow the target rotation speed. This increases a difference between the target rotation speed and the actual rotation speed of the electric rotary machine. After this, when the target rotation speed is adjusted to decrease the difference between the target rotation speed and the actual rotation speed of the electric rotary machine, there is a possible problem for the correction torque obtained on the basis of the charge rate of the target rotation speed to be significantly deviated from its optimal value. This case would cause that the actual rotation speed to be significantly separated from the target rotation speed of the electric rotary machine.